Most facility managers realize that incandescent lamps have the ability to be dimmed smoothly and evenly from full brightness down to zero. Incandescent dimming systems range from small, low wattage units, to ones capable of dimming several kilowatts of lights.

But some facility managers believe that dimming systems don't work with fluorescent lamps. That's a myth that could limit the use of dimming controls with fluorescent lighting systems.

What contributed to this myth is that people have tried to use incandescent dimmers with fluorescent lighting systems. While some dimming resulted, it was inconsistent, resulted in lamp flicker, reduced lamp life, and could not be used over a very wide range of illumination.

Fluorescent lamps cannot be dimmed using incandescent lamp dimmers; they require special, dimming ballasts. Dimming a fluorescent lamp requires a reduction in the lamp arc current while the electrode heater voltage is maintained. Maintaining the electrode heater voltage over reduced light output levels means that the overall efficiency of the lamp will be reduced when it is operated at dimmed levels, but this reduction in efficiency is more than offset by the total reduction in energy use.

The range of dimming that can be achieved in the dimming ballasts for fluorescent lamps depends on the particular ballast design and the type of lamp used. Practically all can be dimmed to 5 percent of the lamp's rated light output. This wide range of dimming makes the systems particularly suitable in a wide range of applications that currently use incandescent lamps.